From the hazy memories of his previous life, Hyuga Kagami knew that the Tenseigan was an evolved form of the Byakugan—a supreme ocular power capable of standing on equal footing with the Rinnegan.
As far as he understood, there were only two known ways to awaken the Tenseigan.
The first was the path taken by Toneri Ōtsutsuki: combining the bloodline of the Moon's Ōtsutsuki branch with the pure main-house bloodline of the Hyuga Clan on Earth, giving birth to the Tenseigan.
The second was to fuse an enormous number of Byakugan together.
Kagami immediately discarded the first option. He was not a main-house heir, nor did he have any way to obtain the lunar Byakugan of Toneri's lineage. As for the second method, the Caged Bird Seal ensured that the Byakugan of branch-family members was destroyed the instant they died or were removed. Relying solely on the main house, it was impossible to gather enough eyes.
Both paths seemed utterly hopeless.
Yet the second method sparked a new line of thought.
Byakugan, Sharingan—every kekkei genkai was, at its core, a manifestation of genes. If he couldn't collect enough eyes, could he instead collect Hyuga genes, fuse them, and evolve the Byakugan into the Tenseigan from within—at the genetic level?
Armed with this bold hypothesis, Kagami devoted himself wholeheartedly to studying genetic research under Orochimaru.
Through relentless experimentation and observation, he made a startling discovery.
Within the DNA of every Hyuga clansman, there existed thirty-three special gene sequences.
Further research revealed that the number of active sequences differed from person to person.
In Kagami's own body, only sequences 17 through 33 were active, while sequences 1 through 16 lay dormant. The dozen or so other Hyuga he examined showed similar results—only a portion of the thirty-three sequences ever activated.
This discovery greatly reinforced his theory.
Kagami even began to suspect that if all thirty-three sequences could be activated simultaneously, any Hyuga might be able to evolve their Byakugan into the Tenseigan.
The idea took root and grew uncontrollably.
Thanks to the ongoing war, Kagami—assigned by Orochimaru to a frontline medical unit—was able to collect large quantities of Hyuga genetic samples with ease. After screening hundreds of specimens, he successfully extracted the active forms of sequences 4 through 16.
Combined with his own naturally active sequences 17–33, he was now missing only three sequences:
1, 2, and 3—and they had to be in their active state.
He had plenty of branch-family genes, but none carried activated sequences 1–3. Inevitably, his gaze turned toward the main house.
However, main-house members rarely went to the battlefield. Even when they did, they were heavily protected—far beyond what a shinobi of Kagami's level could approach. Not once had he succeeded in obtaining a usable sample.
Left with no other option, he asked Orochimaru to intervene.
Orochimaru did not refuse—but even for one of the Legendary Sannin, stealing genetic material from the Hyuga main house was no simple task.
More than a year passed, and the experiment came to a standstill.
Frustrated, Kagami understood one harsh truth: he was nothing more than a small figure struggling to survive. If he wanted to change his fate, he had to seize his own chances. Waiting for fortune to fall from the sky was meaningless.
Just as he began contemplating the yet-unborn Hinata Hyuga, the newest child of the Hyuga main house, Orochimaru—on the eve of his departure—unexpectedly delivered a piece of main-house tissue to him.
As Kagami processed the sample, his thoughts churned.
"Orochimaru's defection should happen any day now. Yet he not only leaves me behind—he even gives me exactly what I need most. What's his goal? Keeping me in the village as a spy?"
Judging by Orochimaru's recent behavior, and by Kagami's fragmented memories of his past life, it was clear that the Sannin's interest in the Byakugan had already waned. Sending this tissue was not for eye research—it was merely to placate him.
With a self-mocking smile, Kagami muttered, "So the Caged Bird Seal isn't completely useless after all."
There was no doubt about it.
The real reason Orochimaru abandoned him was the seal engraved on his forehead. A branch-family member had no right to defect—if Kagami tried, the Caged Bird Seal could kill him instantly. A corpse held no value for Orochimaru.
With the experiment finally back on track, Kagami cast aside all stray thoughts and focused completely on his work.
The tissue Orochimaru provided was exceptionally fresh. Kagami suspected it came from none other than the Hyuga clan head himself—Hyuga Hiashi.
And those were exactly the genes he wanted most.
Thanks to the sample's freshness, extraction went smoothly. What stunned Kagami was the result:
Out of the thirty-three special sequences, twenty-eight were active—including the crucial sequences 1, 2, and 3.
"Twenty-eight active sequences… No wonder he's the head of the clan."
Recalling Hiashi's near–Kage-level combat strength, Kagami quickly accepted the reality.
At his peak, Hiashi was undeniably the strongest warrior of the Hyuga Clan. Possessing the clan's finest genetic makeup was only natural.
Suppressing his amazement, Kagami carefully isolated the long-sought active sequences 1–3.
At last, all active sequences from 1 through 16 were finally in his grasp.
"Whether I can defy fate and seize control of my destiny… it all depends on this moment."
Joy, anticipation, anxiety, hesitation—countless emotions surged through him, leaving his mind briefly blank.
He wanted to roar to the heavens, to release the fear and pressure he had carried for years.
But the cold gaze of the One-Eyed Viper on his shoulder forced him to suppress every impulse.
Exhaling softly, Kagami steadied himself.
With calm precision, he poured the extracted gene solution into a small insulated vial, then sealed it carefully inside a scroll.
Orochimaru's defection was bound to shake the entire village.
To avoid being implicated, Kagami still had a great deal of work to do—starting with this laboratory.
Every trace of his presence, especially any clue related to the special-sequence fusion experiment, had to be erased completely before the village began its investigation.